CONFUSED ABOUT PROJECTORS? Let us help clarify the situation here with a brief run down of some
projector technology explained.
PROJECTOR RESOLUTION:
This is the native resolution and is measured in pixels. A pixel is
an abbreviation for "picture element" and is the smallest
unit that a screen is capable of displaying. These are built up in a
grid which then constitutes the picture. There are many different formats
out there with two aspect ratios:- 4:3 (standard TV), 16:10 (widescreen
format). For standard aspect ratios SVGA & XGA are the the two most
common projector resolutions. SXGA & UXGA also exist although only
in higher end projectors at the moment. The table below shows the pixel
size of all the resolutions. Widescreen formats currently available
are WXGA, WXGA+, WSXGA+ and WUXGA. These also tend to be be more expensive
units.
RESOLUTIONS IN PIXELS |
|
SVGA is 800 x 600 XGA is 1024 x 768 SXGA is 1280 x 1024 SXGA+ is 1400 x 1050 UXGA is 1600 x 1200 |
WXGA is 1280 x 800 |
ANSI LUMENS: This is the measurement
of brightness as defined by the American National Standards Institute
(ANSI). It can be used as a guide for brightness but the rating is not
absolute. We have found there to be a large variation in actual perceived
brightness between units, with decent 1500 lumens projectors being effectively
brighter than cheap 2500 lumens units. For this reason we only stock
high quality projectors. When we sell projectors we recommend quality
over bargain prices, although we can supply any make or model desired.
KEYSTONE / KEYSTONE CORRECTION: The keystone effect happens when
the projector is not placed optimally to the screen. The lens should
be on a line drawn at a right angle out from the centre of the screen.
Optimal horizontal alignment is setting the bottom of the lens and at
bottom of the screen in line. If, for instance, the projector is placed
below the screen the resulting image will be wider at the top than the
bottom which is known as vertical keystoning. This can be corrected
digitally if the projector has the facility. All our hire stock has
at least vertical keystone adjustment. Some of our models also allow
for horizontal keystone adjustment. Please ask if you are unsure.
PROJECTOR - DISTANCE TO SCREEN
& ZOOM LENS: For a 6 foot wide
image the projector should be placed 12 feet back, ie. twice as far
back as the image is wide. This can be adjuested using the zoom lens.
Most modern projectors will also allow digital zooming for further adjustment
if required.
PROJECTION TECHNOLOGIES - LCD, DLP & LCOS:
These are the methods used to convert your image from an electrical
/ digital signal into an image. There are three competing technologies
at this time which utilise different methodology to convert the light
emitted by the internal lamp into a colour image on the screen. LCD
projectors split white light into its primary component colour streams
of red, green & blue using dichroic mirrors which are then shone
through the LCD panels & recombined. By controlling the level of
R, G & B on each pixel the colour of that pixel is created. DLP
uses a grid of tiny mirrors, each corresponding to a pixel, which allow
a given percentage of light through per pixel. This light is then shone
through a rotating RGB colour wheel to bring colour into the equation.
High end DLP projectors can use RGB split technology. LCOS is the newest
of the three which is Liquid crystal on Silicon. It is almost a hybrid
between the two technologies. At this time LCD is by far the market
leader, with the brightest & clearest images although DLP is used
in the home theatre market due to its improved contrast ratio. DLP can
can problematic for some viewers due to the so-called Rainbow effect
resulting in headaches & eystrain. LCOS is a relative newcomer to
the field and may well go on to become the future of projection technology.
We stock LCD projectors at this time although we can sell or provide
rental DLP & LCOS units upon request.
PROJECTOR CONTROL:
Most modern projectors will have an infrared remote offering at least
basic functionality, plus full on board control. It is very common to
also have USB control inputs which allow projector control from from
a computer (appropriate driver disks will be required). Ethernet network
control is also possible. Certain projector models have on board DVD
players, and or MPEG players meaning that an external input is unnecessary.
PROJECTOR INPUTS: Most projectors
will accept a number of different inputs. PAL, SECAM & NTSC are
generally accepted. Composite & S-Video are generally accepted as
are computer monitor style inputs on 15 pin d-sub connectors. DVI (Digital
Video Interface) is now widely accepted.